Why aren't these faces extruded as the tutorial video?
You have a lot of overlapping vertices which seem to be effecting the scaling operation.

To remove these:


In Edit mode select All of the model.
Open the Vertex menu.
Select the Merge Vertices.
Select the By Distance option.


At the bottom of the screen you will see how many vertices have been removed.



Now re select the 8 faces, and they will scale as shown in the video.